Three major airlines in the U.S., American Airlines, Delta Air Lines, and Frontier Airlines, have agreed to each pay thousands of dollars for failing to follow airline consumer protection rules.

Each airline was fined for a slightly different reason according to the U.S. Transportation Department. American was fined $250,000 for failing to make timely refunds to passengers in early 2015, while Delta was fined $200,000 for filing inaccurate baggage reports. Finally, Frontier was fined $400,000 for violating oversales and disability rules.

American spokeswoman, Shannon Gilson, responded to the news release stating, “We took proactive steps to address refund delays some customers experienced in 2015 due to a systems integration issue after the merger with US Airways, including investments to improve processing times.”

Delta’s baggage issue dates even further back, with the issue stemming from a failure to properly report all baggage claims from 2012 to 2015.

The airline responded on Saturday by saying that once it was made aware that its baggage policy didn’t comply with the government’s rules, it updated its policy and has since invested in ways to provide more transparency on its bags such as through its FlyDelta app available on most smartphones.

With the largest portion of the fines being directed at Frontier Airlines, it is no surprise that the U.S. Transportation Department provided a much more detailed response on its violations.

According to its press release, “The Department found that Frontier failed to seek volunteers before bumping passengers involuntarily, failed to provide bumped passengers the required written notice describing their rights, and failed to provide proper compensation to passengers in a timely manner, in violation of DOT rules.”

The department continued, stating that “In addition, Frontier failed to provide passengers with a disability prompt and adequate wheelchair assistance in enplaning and deplaning aircraft and moving within the terminal, and did not adequately respond to complaints filed by passengers with disabilities.”

Frontier, which has gone through many iterations since its founding in 1994, has struggled in recent years with providing sufficient customer service given many delays and cancellations, as it has attempted to be an ultra low-cost carrier while still maintaining connecting service at its hub in Denver.

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